Separation of natural gases



G. E. HAYS SEPARATION OF NATURAL GASES UOLVHVdIS EISVHd Nov. l, 1966Original Filed Jan. 25, 1962 INVENTOR.

G. E. HAYS Y, f ,Q1/( Il? l iLLL/yj ATTORNEYS E om 1^ United StatesPatent O 3,282,060 SEPARATION F NATURAL GASES George E. Hays,Bartlesville, Okla., assignor to Phillips Petroleum Company, acorporation of Delaware Continuation of application Ser. No. 168,667,Jan. 25, 1962. This application Nov. 9, 1965, Ser. No. 514,736 6 Claims.(Cl. 62-24) This application is a continuation -of Serial No. 168,667,tiled January 25, 1962, of George E. Hays.

This invention relates to method and apparatus for separating gases. Inoneaspect, the invention relates to method and apparatus for recovery ofhelium from gas wherein, in a multiple-stage condensation-phaseseparation system, helium losses in a removed liquid stream are reducedby stripping the stream. In another aspect, the invention relate-s tomethod and appara-tus for reducing loss of dissolved helium in a liquidstream withdrawn from a multiple-stage condensation-phase separation gasfractionation system by stripping the withdrawn stream utilizing inindirect heat exchange the stream prior to its stripping.

The value of helium as an inert atmosphere, a component of an artificialbreathing medium, a lifting gas, and other diverse uses has been known.The world supply of naturally-available helium is limited to very fewgeographical locations, most of which are within the continental UnitedStates, and is further limited so far as is presently known as being aminor constituent of natural gas. Various eiiorts have been made in thepast to recover the helium from such a gas mixture economically, andhave met wit-h greater or lesser success.

Accordingly, it is an object of my invention to provide method andapparatus for separating a gas mixture. It is another yobject of myinvention to provide economical method and apparatus for recoveringhelium from a gas mixture containing helium. It is another obje-ct of myinvention to yprovide method and apparatus for recovering increasedamounts of helium from natural gas. It is a still further `object ofthis invention to recover helium from the gaseous phase of condensednatural gas.

Other aspects, objects and the several advantages o my invention willbecome apparent from a study of this disclosure, the drawing, and theappended claims.

According to my invention, there are provided method and apparatus forseparating a gas containing helium which comprises cooling the gas tocondense liquid, separating condensed liquid from the gas, expanding theremaining gas stream to produce additional liquid, reboiling .the liquidso as to strip helium therefrom, removing the stripped liquid as aproduct, further cooling and expanding gases resulting from thestripping so as to produce additional liquid, separating the additionalliquid, and recovering the remaining gas as a crude helium product.

Reference is now made to the drawing, which is a flow diagram lof apreferred embodiment of my invention, for a more complete understandingof the invention.

Raw natural gas, which can have previously been treated for removal ofundesired constituents, is passed by Way of conduit 1 through a cooler 2to a phase separatorl 3. Liquids, such as natural gas liquid, which werecondensed in cooler 2 are Withdrawn from this phase separator by Way ofconduit 4 to further utility. Uncondensed vapors are passed overhead byway of conduit 5 through a cooler 6 to a second phase separator 7.Liquids, such as a liquefied residue gas, which were condensed in cooler6 are withdrawn from this phase separator by way of conduit 8 to furtherutility. Remaining uncondensed vapors are passed overhead by way ofconduit 9 through a cooler 1t) to a heat-exchange bundle 11 PatentedNov. 1, 1966 in the combined separator-stripper 12. Vessel 12 servesboth as a vapor-liquid phase separator, separating out liquids condensedby cooler 10, and as a stripper to remove most of the dissolved heliumfrom the condensed liquid. This condensed liquid residue gas, which isprimarily methane, is removed by way of conduit 13 to further utilityand can, if desired, be combined with the stream in conduit 8. Thestripping action is abetted by a series of vapor-liquid contactingdevices 14, which can be, for example, bubble-cap or sieve trays.Instead of trays, stripper 12 may contain packing such as rings,saddles, etc. After the mixed vapor-liquid stream in conduit 9 has givenup some of its heat in exchanger 11, it is passed by way of conduit 15through a cooler 16 and an expander 17. Coolers 10 and 16 can bealternative, i.e., either one can be used without the other, or both canbe used as shown in the drawing. This will depend, as is known in theart, upon the temperatures and pressures of the streams desired andavailable and upon the surface areas Iof the respective coolers,although according to a presently-preferred embodiment of the invention,cooler 16 is not needed. Expander 17 can be a throttling valve, turbine,or other means of expanding a gas and its use result-s in additionaltemperature lowering of the stream in conduit 15. The expanded stream ispassed into an upper portion of vessel 12 Where the condensed portion isreuxed and stripped as previously discussed. Vapors resulting from theuncondensed portion of stream 15 and from the stripping are collectedand passed overhead by way lof conduit 18 through cooler 19 to a secondexpander 20. This expander can be similar to the one previouslydescribed; the action of cooler 19 and expander 20 eliect condensationof additional liquid in stream 18, and the resulting stream is passed tovapor-liquid phase separator 21. The condensed liquid is withdrawn fromphase separator 21 by way of conduit 22 to further utility, for example,as a fuel gas, and the residual uncondensed vapors are withdrawn fromseparator 21 by way of conduit 23. These residual vapors comprise acrude helium product and can be utilized as such or further treated asdesired.

Although, as `shown on the drawing, it is presently preferred that theheat for reboiling stripper 12 be furnished by stream 9 in order thatthe latter stream is thereby cooled, it is :also contemplated thatstripping heat for vessel 12 be furnished from an external stream.Accordingly, conduits 24, 25 and 26 are shown along with theirassociated block valves so that gas in conduit 9 can pass by way ofconduit 26 directly to cooler 16, by-passing heat exchange 'bundle 11.In this instance, heat is supplied to -bundle 11 by a suitable uid byway of conduits 24 and 25.

The source of cooling on the cold side of coolers 2, 6, 10 and/or 16,and 19 can be an external source of refrigeration, although it ispresently preferred that the various product streams serve as :a sourceof cold. For example, streams 22 and/or 23 can be passed sequentiallythrough the cold side of coolers 19, 16 and/ or `10, 6 and 2; stream 13can be .passed sequentially through coolers 16 :and/or 10, 6 and 2; andstream 8 can be passed sequentially through coolers 6 and 2. Stream 4can also be passed through cooler 2. Use of these product streams tocountercurrently cool the various stages has been left off the drawingfor sake of clarity. Phase separators 3, 7, 12 and 21 are operated toseparate vapor from liquid as is known in the art and can utilize, forexample, valves in the liquid etliuent streams therefrom controlled inresponse to liquid level therein.

The following specific example will serve to more fully illustrate myinvention. Compositions given are for the total mixture.

rs .a 4

EXAMPLE Composition, mol percent Stream No. Temp., Press., F. p.s.l.a.

He N1 .CH4 CgTq CgHs 04H10 CsImy 1 (after cooler 2) -80 345 0.75 14.8471. 72 6. 19 4. 09 1. 68 0. 73 4 -130 21 Trace 1. 40 26. 52 2l. 27 30.38 14.04 G. 39 -165 343 0.84 16. 52 77. 46 4. 29 0. 77 -0.11 0. 01 -180224 0. 02 5. 47 82. 52 9. 86 1, 83 0. 27 0. 03 -197 340 1. 44 24. 47 73.82 0. 27 Trace, -207 225 0. 01 16. 05 83. 59 0. 35 Trace (after expander17) 1 -212 225 1. 44 24. 47 73. 82 0. 27 Trace 18 (after expander 20).-294 75 G. 68 55. 65v 22 -294 75 0. 03 57. 33 -294 75 52. 38 43. 27

1 Cooler 16 is not used in this example.

In the example, separator-stripper 12 has :a top section 3% feet indiameter by 5 feet high and a bottom section 81/2 feet in diameter by 8feet high; the bottom section may contain 9 trays on 8" spacing and isreferred to in the drawing as item 14. Alternately, the bottom sectionmay contain about 5 feet of packing such as rings or saddles. The heatexchange area of bundle 11 is 3350 sq. feet.

Reasonable variation and modification are possible within the scope ofthis disclosure, the drawing, and the appended claims to the inventionthe essence of which is .that there are provided a method :and apparatusfor separation of helium from a gaseous mixture by cooling andseparating out liquid from the mixture, further cooling the uncondensedgases to produce additional liquid, reboiling the condensed liquid tostrip dissolved helium therefrom, and further cooling and phaseseparating remaining uncondensed gases to recover .a helium product.

I claim:

1. Gas separation apparatus comprising first indirect cooling means,conduit means communicating between a supply of mixed gases containinghelium and said first cooling means, first vapor-liquid phase separatormeans, conduit means communicating between said first cooling means andsaid first separator means, conduit means communicating with fa lowerportion of said first separator means and adapted to withdraw a liquidtherefrom, second indirect cooling means, conduit means communicatvingbetween said second cooling means and an upper means communicatingbetween said indirect heat exv change means and said lirst expansionmeans, conduit means communicating between said first expansion meansand a region above said vapor-liquid contacting means and adapted topass a mixture of vapor and liquid from said first expansion means ontosaid vapor-liquid contacting means, conduit means communicating with aregion Ibelow said indirect heat exchange means and adapted to withdrawa stripped liquid from said region, second expansion means, conduitmeans communicating between said second expansion means and a regionabove said vapor-liquid contacting means and adapted to pass a vaporfrom said region above said vapor-liquid contacting means to said secondexpansion means, second phase separator means, conduit meanscommunicating between said second expansion means and said second phaseseparator means, conduit means adapted to withdraw a liquid from a lowerregion'of said second phase separator means, and conduit means adaptedto withdraw a crude heliumcontaining vapor product from an upper regionof said second phase separator means.

2. The method of recovering helium from a mixture of gases whichcomprises:

(a) cooling the mixture of gas to effect a separation of a liquid phase;

(b) further cooling the gas phase to partially liquefy the gas;

(c) passing said partially liquefied gas through a reboiler zone of aseparator-stripper land then to further cooling before expansion andintroduction into said stripper for refiuxing and stripping;

(d) removing the gas overheadfrom the stripper for cooling; expansionand separating into a liquid fuel gas phase and a crude helium product.

3. The method of recovering helium from a mixture of gases whichcomprises:

(a) cooling the mixture of gas to effect a separation of a liquid phase;

(b) further cooling the gas to effect a second separation of a liquidphase;

(c) further cooling the gas phase to partially liquefy :the gas;

(d) passing said partially liquefied gas through a reboiler zone of aseparator-stripper and then to further cooling before expansion andintroduction into said stripper for refluxing and stripping;

(e) removing the gas overhead from the stripper for cooling, expansionand separating into a liquid fuel gas phase and a crude helium product.

4. The method of claim 3 further comprising the step of combining theliquid phase of the stripper with the liquid separated in said secondseparation step.

5. The method of claim 4 wherein said mixture of gases is raw naturalgas.

l6. The method of recovering helium from a mixture of gases whichcomprises:

(a) cooling the mixutre of gas to effect a separation of a liquid phase;

(b) further cooling the gas phase to partially liquefy the gas;

(c) passing said partially liquefied gas through a reiboiler zone of aseparator-stripper before expansion and introduction into said stripperfor refluxing and Stripping;

(d) removing the gas overhead from the stripper for cooling, expansionand separating into a liquid fuel gas phase anda crude helium product.

References Cited by the Examiner UNITED STATES PATENTS 1,529,625 3/ 1925Rafferty et al.

1,664,412 4/1928 Haynes 62-31 X 1,676,225 7/ 1928 Tolman 62-22 1,723,4258/ 1929 Jaubert.

1,850,529 3/1932 Bottoms a 62-27 2,012,080 8/ 1935 De Baufre.

2,557,171 6/1951 Bodle et al.

2,582,148 1/1952 Nelly 62-23 X 2,940,271 6/ 1960 Jackson 62-23 NORMANYUDKOFF, Primary Examiner.

V. W. PRETKA, Assistant Examiner.

1. GAS SEPARATION APPARATUS COMPRISING FIRST INDIRECT COOLING MEANS,CONDUIT MEANS COMMNICATING BETWEEN A SUPPLY OF MIXED GASES CONTAININGHELIUM AND SAID FIRST COOLING MEANS, FIRST VAPOR-LIQUID PHASE SEPARATORMEANS, CONDUIT MEANS COMMUNICATING BETWEEN SAID FIRST COOLING MEANS ANDSAID FIRST SEPARATOR MEANS, CONDUIT MEANS COMMUNICATING WITH A LOWERPORTION OF SAID FIRST SEPARATOR MEANS AND ADAPTED TO WITHDRAW A LIQUIDTHEREFROM, SECOND INDIRECT COOLING MEANS, CONDUIT MEANS COMMUNICATINGBETWEEN SAID SECOND COOLING MEANS AND AN UPPER PORTION OF SAID FIRSTSEPARATOR MEANS AND ADAPTED TO PASS A VAPOR FROM SAID FIRST SEPARATORMEANS TO SAID SECOND COOLING MEANS, COMBINED SEPARATOR-STRIPPER MEANSCOMPRISING VAPOR-LIQUID CONTACTING MEANS DISPOSED ABOVE AN INDIRECT HEATEXCHANGE MEANS, CONDUIT MEANS COMMUNICATING BETWEEN SAID SECOND COOLINGMEANS AND SAID INDIRECT HEAT EXCHANGE MEANS, FIRST EXPANSION MEANS,CONDUIT MEANS COMMUNICATING BETWEEN SAID INDIRECT HEAT EXCHANGE MEANSAND SAID FIRST EXPANSION MEANS, CONDUIT MEANS COMMUNICATING BETWEEN SAIDFIRST EXPANSION MEANS AND A REGION ABOVE SAID VAPOR-LIQUID CONTACTINGMEANS AND ADAPTED TO PASS A MIXTURE OF VAPOR AND LIQUID FROM SAID FIRSTEXPANSION MEANS ONTO SAID VAPOR-LIQUID CONTACTING MEANS, CONDUIT MEANSCOMMUNICATING WITH A REGION BELOW SAID INDIRECT HEAT EXCHANGE MEAND ANDADAPTED TO WITHDRAW A STRIPPED LIQUID FROM SAID REGION, SECOND EXPANSIONMEANS, CONDUIT MEANS COMMUNICATING BETWEEN SAID SECOND EXPANSION MEANSAND A REGION ABOVE SAID VAPOR-LIQUID CONTACTING MEAND AND ADAPTED TOPASS A VAPOR FROM SAID REGION ABOVE SAID VAPOR-LIQUID CONTACTING MEANSTO SAID SECOND EXPANSION MEANS, SECOND PHASE SEPARATOR MEANS, CONDUITMEANS COMMUNICATING BETWEEN SAID SECOND EXPANSION MEANS AND SAID SECONDPHASE SEPARATOR MEANS, CONDUIT MEANS ADAPTED TO WITHDRAW A LIQUID FROM ALOWER REGION OF SAID SECOND PHASE SEPARATOR MEANS, AND CONDUIT MEANSADAPTED TO WITHDRAW A CRUDE HELIUMCONTAINING VAPOR PRODUCT FROM AN UPPERREGION OF SAID SECOND PHASE SEPARATOR MEANS.